As a means to reduce traffic, many cities are encouraging drivers to carpool, such as by providing carpool only lanes, which are generally less crowded, or reducing costs otherwise required in full by single occupant vehicles. Each city can set the required number of occupants to qualify as a carpool for receiving carpool benefits. However, many cities do not have means to enforce the carpool status, other than using an on-duty patrol person to watch the cars as they pass by and manually count the number of occupants.
If a violation is identified, the patrol officer must pull the driver of the violating vehicle off the road and issue a citation. Using employee resources can be time consuming and costly for the city. Additionally, only a sample of vehicles are monitored based on times when a patrol person is available for enforcement. Therefore, violations may not be strictly monitored due to a lack of enforcement.
Attempts to automate carpool enforcement and tolling have been made, but are generally inadequate. For example, high-occupancy vehicle (HOV) lanes are restricted for exclusive use by vehicles that include the designated number of passengers, including the driver. Cars that do not have a minimum number of designated passengers may receive a ticket, such as in the mail. Cameras are used to enforce the occupancy requirement by taking photographs of passing vehicles in the HOV lanes and the photographs are subsequently analyzed to determine occupancy. However, in a photograph, occupants can be occluded by objects in the car or by glare off the vehicle windows. For example, occupants in the back seat can be blocked by front seats in the vehicle when the camera is positioned in front of the car. Further, photographs are influenced by glare, which can obscure occupants in the vehicle. Thus, use of a camera is an unreliable and inaccurate means for determining occupancy.
Additionally, some cities use FasTrak® lanes, a registered trademark of San Joaquin Hills Transportation Corridor Agency and Foothill/Eastern Transportation Corridor Agency Joint Powers Agency of California, that allow vehicles with the required carpool occupancy to drive in a particular lane and to be charged accordingly based on a toll tag that is mounted on a vehicle's windshield. Subsequently, as the vehicle passes through the automatic tolling area, the rate charged is based on the lane in which the vehicle is located. Thus, the FasTrak® system relies on drivers to truthfully select the correct lane based on vehicle occupancy. The carpool discounts can be enforced using cameras, as described above, which may not be completely reliable due to positioning of the camera and glare from the camera flash or sun. Further, designating particular lanes for carpools is undesirable since the carpool lanes are generally located to one side of the road and vehicles that do not satisfy the carpool requirements may have to cross multiple lanes of traffic to make a desired turn after passing through the tolling area.
Finally, High-Occupancy Toll (HOT) lanes are designated carpool lanes that allow vehicles that do not qualify as a carpool to pay a predetermined fee and utilize the carpool lanes via a pass installed on a window of the vehicle. A switchable pass allows drivers to turn on or off the pass based on a number of occupants in the vehicle, which relies on an honor system for charging single drivers. Again, use of and payment for the carpool lanes by non-carpool vehicles are generally only enforced by an honor system, manual enforcement, or via a camera, each of which is can be unreliable as described above.
Therefore, there is a need for determining a number of occupants within a vehicle. Preferably, the determined occupancy is used for automatic carpool enforcement and tolling.